• Journal of the Korean Society for Heat Treatment
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• v.3 no.2
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• pp.1-9
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• 1990

Since the reverse shape memory effect(RSME) was reported in a CuZnAl alloy, further study has been done on the mechanism of this phenomenon and reported that it occurs by the bainitic transformation. But the present authors revealed in the previous work that the RSME in a B2 CuZnAl alloy is not caused by the shear process involved in the bainitic transformation and also that the RSME takes place as the remaining ${\alpha}^{\prime}{_2}$ phase, which is two-step transformed strain induced martensite, is newly transformed into ${\alpha}$ phase. In order to provide further evidence in supporting the facts, thus, more detailed investigations have been carried out in a $DO_3$ CuZnAl alloy.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.5
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• pp.725-731
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• 2023

In this study, the harmless crack size was evaluated using carburized, quenched-tempered SCM822H steel. The possibility of detecting cracks that reduce the fatigue limit by non-destructive inspection was evaluated. The conclusions obtained are as follows. The retained austenite of surface was reduced by SP. About 35% and 65% of the retained austenite on the surface were transformed into strain-induced martensite, increasing the hardness by 79HV and 122HV over the as-received material. The maximum compressive residual stresses introduced on the surfaces were -695 MPa and -688 MPa, respectively. The fatigue limit increased by 1.48 times and 1.67 times, respectively, compared to the as-received material. The harmless crack size of SP specimen was determined differently depending on the shot ball size.

• Journal of Powder Materials
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• v.26 no.5
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• pp.389-394
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• 2019

In the present study, we have investigated the effect of sintering process conditions on the stability of the austenite phase in the nanocrystalline Fe-5wt.%Mn-0.2wt.%C alloy. The stability and volume fraction of the austenite phase are the key factors that determine the mechanical properties of FeMnC alloys, because strain-induced austenite-martensite transformation occurs under the application of an external stress at room temperature. Nanocrystalline Fe-5wt.%Mn-0.2wt.%C samples are fabricated using the spark plasma sintering method. The stability of the austenite phase in the sintered samples is evaluated by X-ray diffraction analysis and hardness test. The volume fraction of austenite at room temperature increases as the sample is held for 10 min at the sintering temperature, because of carbon diffusion in austenite. Moreover, water quenching effectively prevents the formation of cementite during cooling, resulting in a higher volume fraction of austenite. Furthermore, it is found that the hardness is influenced by both the austenite carbon content and volume fraction.